18 research outputs found
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Improvements to the on-line mass separator, RAMA, and the beta-delayed charged-particle emission of proton-rich sd shell nuclei
To overcome the extreme difficulties encountered in the experimental decay studies of proton drip line nuclei, several techniques have been utilized, including a helium-jet transport system, particle identification detectors and mass separation. Improvements to the ion source/extraction region of the He-jet coupled on-line Recoil Atom Mass Analyzer (RAMA) and its target/ion source coupling resulted in significant increases in RAMA efficiencies and its mass resolution, as well as reductions in the overall transit time. At the 88-Inch Cyclotron at LBNL, the decays of {sup 31}Cl, {sup 27}P and {sup 28}P, with half-lives of 150 msec, 260 msec and 270.3 msec, respectively, were examined using a he-jet and low-energy gas {Delta}E-gas {Delta}E-silicon E detector telescopes. Total beta-delayed proton branches of 0.3% and 0.07% in {sup 31}Cl and {sub 27}P, respectively, were estimated. Several proton peaks that had been previously assigned to the decay of {sup 31}Cl were shown to be from the decay of {sup 25}Si. In {sup 27}P, two proton groups at 459 {+-} 14 keV and 610 {+-} 11 keV, with intensities of 7 {+-} 3% and 92 {+-} 4% relative to the main (100%) group were discovered. The Gamow-Teller component of the preceding beta-decay of each observed proton transition was compared to results from shell model calculations. Finally, a new proton transition was identified, following the {beta}-decay of {sup 28}P, at 1,444 {+-} 12 keV with a 1.7 {+-} 0.5% relative intensity to the 100% group. Using similar low-energy detector telescopes and the mass separator TISOL at TRIUMF, the 109 msec and 173 msec activities, {sup 17}Ne and {sup 33}Ar, were studied. A new proton group with energy 729 {+-} 15 keV was observed following the beta-decay of {sup 17}Ne. Several discrepancies between earlier works as to the energies, intensities and assignments of several proton transitions from {sup 17}Ne and {sup 33}Ar were resolved
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Improvements to the On-Line Mass Separator, RAMA< the Beta-Delayed Charged-Particle Emission of Proton-Rich sd Shell Nuclei
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Additional Results from the Beta-delayed Proton Decays of {sup 27}P and {sup 31}Cl
Beta-delayed proton decays of the nuclides P-27 and Cl-31 were measured using the helium-jet recoil collection technique and low-energy particle identification detector telescopes. In P-27, two new proton groups at 466+/-3 keV and 612+/-2 keV, with intensities of 9+/-2% and 97+/-3% relative to the main (100%) group at 731+/-2 keV, were discovered. Additionally, during the P-27 experiments, a new proton transition was identified following the beta decay of P-28. This group, at a proton energy of 1452+/-4 keV, had a 2+/-1% intensity relative to the 100% group at 679+/-1 keV. A total P-27 beta-delayed proton branch of 0.07% was estimated. The experimental Gamow-Teller beta-decay strengths of the observed transitions from P-27 were compared to results from shell model calculations. A search for new proton transitions in Cl-31, the next member of this A = 4n + 3, T-z = -3/2 series, was unsuccessful. However. several proton peaks that had been previously assigned to Cl-31 decay were shown to be from the decay of Si-25
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Improvements to the On-Line Mass Separator, RAMA< the Beta-Delayed Charged-Particle Emission of Proton-Rich sd Shell Nuclei
Recommended from our members
Additional results from the beta-delayed proton decays of {sup 27}P and {sup 31}Cl
The experimental investigation of the decays of proton-rich light nuclei has provided a wealth of spectroscopic information. This includes details of energy levels, spins, isospins, masses, half-lives and other decay properties. In light nuclei, total beta decay energies rapidly increase as one moves away from the valley of beta-stable nuclides towards the proton drip line. This opens up decay modes, such as beta-delayed proton and beta-delayed alpha emission, which are very sensitive probes of nuclear structure. There have been several recent articles that review the decay properties of proton drip-line nuclei. The beta decays of proton-rich light nuclei (with T{sub z} {le} -1/2) are characterized by two general features. The first is a fast superallowed Fermi transition to the isobaric analog state (IAS) in the beta daughter. If the IAS is above the proton separation energy, the beta-decaying precursor nuclide is classified as a strong beta-delayed proton emitter. The A = 4n+1, T{sub z}=-3/2 series of nuclei from {sup 17}Ne to {sup 73}Sr (with the exception of the unobserved member {sup 69}Kr), are all strong {Beta}p emitters. In contrast, the A = 4n, T{sub z}=-1 series of nuclei, from {sup 24}Al to {sup 48}Mn are designated as weak {Beta}p emitters since the IAS in the beta daughters is bound with respect to proton emission